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Title:Impact of laboratory simulated aging on asphalt concrete flexibility
Author(s):Zhu, Zehui
Advisor(s):Al-Qadi, Imad L.; Ozer, Hasan
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Asphalt concrete
Flexibility index
Long-term aging
Aging rate
Mixture design
Abstract:The aging of asphalt materials is considered an important factor contributing to the deterioration of asphalt concrete (AC) pavements. Asphalt binder aging is a combination of various complex mechanisms that affect its rheological properties causing AC to become stiffer and more brittle. As a result of aging, the resistance of AC pavements to various forms of cracking including fatigue, thermal, and/or block is reduced. Hence, AC aging presents challenges for preserving an adequate level of pavement serviceability. Therefore, it is critical to understand the effect of aging on AC pavement cracking development and identify the effect of AC mix design parameters on the aging rate. A wide range of AC mixes were investigated in this study using the Illinois Flexibility Index Test (I-FIT) after the specimens were subjected to various lab-simulated long-term aging conditions. The flexibility index (FI), an outcome of the I-FIT and a measure of the AC flexibility. decreases consistently after long-term aging. This effect is primarily due to changes in the post-peak slope, an indication of crack propagation speed. The impact of aging on various AC mixtures varies and results in different FI deductions because of the mix type and aging condition. Simple and multiple linear regression were used to analyze the impact of mix design parameters on AC aging rate. The effect of voids in mineral aggregate (VMA), low-temperature performance-grade (PG), asphalt binder replacement (ABR), AC mix type, water absorption of the aggregate blend, and effective asphalt binder content was found to be significant. Several aging levels were examined using a conventional oven and utilizing both compacted and loose AC mixes. The various aging levels were compared to the standard five-day aging at 85oC (5D/85C). The study found that aging compacted I-FIT specimens at 3D/95C is practical and is equivalent to that at 5D/85. Additionally, because the parameters impacting aging at 1D/95C and 3D/95C are the same and have the same trend, 1D/95C may be used as an initial indicator for long-term aging.
Issue Date:2018-12-05
Rights Information:Copyright 2018 Zehui Zhu
Date Available in IDEALS:2019-02-08
Date Deposited:2018-12

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